Control of ferulic acid and 4-vinyl guaiacol in brewing

Phenolic acids in beer are important because they can be decarboxylated to phenols, which usually impart off-flavours. An improved high performance liquid chromatographic system was used to monitor phenolic acids and phenols during the brewing process. Ferulic acid was the most significant phenolic acid found in beers prepared from malted barley. Extraction of ferulic acid from malt involved an enzymatic release mechanism with an optimum temperature about 45 degrees C. Mashing-in at 65 degrees C significantly decreased the release of free ferulic acid into the wort, Wort boiling produced 4-vinyl guaiacol by thermal decarboxylation, in amounts (0.3 mg/L) close to its taste threshold, from worts that contained high contents of free ferulic acid (>6 mg/L), The capacity of yeasts to decarboxylate phenolic acids (Pof(+) phenotype) was strong in wild strains of Saccharomyces and absent in all lager brewing yeast and most ale brewing yeasts. Some top-fermenting strains, especially those used in wheat beer production, possessed a weak decarboxylating activity (i.e. Pof(+)). During storage of beers there were appreciable temperature-dependent losses of 4-vinyl guaiacol. These results indicated that the production of 4-vinyl guaiacol is amenable to close technological control.